A change in temperature is known to affect the deformation properties of a clay specimen. In order to study the effect quantitative y and its dependence on clay type a number of oedometer tests were carried out. Conventional incremental oedometer tests as well as constant-rate-of-strain tests were used. Test results clearly show that the preconsolidation pressure decreases with increasing temperature; the compression modulus is little affected. Five different clays were tested, and the change in preconsolidation pressure was found to be larger for higher clay content of the specimen. The research shows that laboratory testing at different temperatures gives the necessary information for the calculation of temperature induced settlements.

For the past five years or so Hall effect semiconductors have been increasingly used in the geotechnical engineering laboratories at the University of Surrey. They have been incorporated as sensing elements in local radial and axial strain measuring devices, for the small-strain instrumentation of triaxial specimens, and in small diameter boundary normal and shear stress cells. Triaxial internal load cells are currently being built incorporating Hall effect semiconductors. This paper describes the Hall effect principle and the methods of configuring magnet/sensor systems to achieve suitable measuring systems. Some geotechnical instruments built at the University of Surrey are detailed, and their characteristics discussed. The calibrations of the instruments described in the paper show a performance generally at least as good as might be expected from some commercially available instruments. Hall effect semiconductors are shown to be of use in a range of situations where displacement can form the basis of measurement. The displacements measured can vary from as little as 5 µm to as much as 10 mm, and the best repeatability so far obtained has been of the order of 1/100 of a micrometre.

An experimental procedure for nondestructive, specimen-specific measurement of membrane penetration volume change is presented. The procedure involves measurement of the annular volume between two membranes as an outer ported membrane is “consolidated” over the deformed surface of an inner membrane. With minor adjustments for the effects of membrane thickness and pore-pressure change, the double membrane procedure yields the membrane penetration volume change behavior of the inner membrane. The procedure is conducted in such a manner that the effective stresses in the specimen remain unchanged, allowing the specimen to be tested after its membrane penetration characteristics have measured. Agreement with measured membrane penetration behavior has been very good.

The nonlinear subgrade reaction method (P-y curves) is widely used for the design of laterally loaded piles. This method replaces the soil reaction with a series of independent nonlinear Winkler springs. A preliminary semi-empirical approach for the determination of P-y curves using data obtained from a flat dilatometer test (DMT) is presented and evaluated. A brief description of the equipment, testing procedures, and the theory that enables the family of P-y curves to be determined are presented. The P-y curves are used as input for an existing finite-difference program, which calculates pile deflection versus depth at various lateral loads. An evaluation of the proposed method is presented using data from three full-scale laterally loaded test piles. A comparison and discussion are provided between the predicted and measured behavior of the piles during lateral loading.

The American Association of State Highway and Transportation Officials (AASHTO) approved the establishment of the AASHTO Accreditation Program (AAP) in February 1988 and the first laboratory was accredited in June 1988. The objective of the AAP is to provide a mechanism for formally recognizing the competency of construction materials testing laboratories to carry out specific tests on soils, asphalt cements, cutback asphalts, emulsified asphalts, bituminous concrete mixtures, concrete aggregates. AAP is structured to comply with ASTM Standards, Guide for Laboratory Accreditation Systems (E 994) and Practice for Generic Criteria for Use in the Evaluation of Testing and Inspection Agencies (E 548), and International Standards Organization (ISO) Guide 25. AASHTO has assigned responsibility for administering the program to its Highway Subcommittee on Materials. Information on the program scope, operational procedures, and current status are given.